Staking is the process of connecting two components by creating an interference fit between the two pieces. One workpiece has a hole in it while the other has a protrusion that fits within the hole. The protrusion is often undersized so that it may slip into the hole. A punch may then be used to compress the boss radially and form an interference fit between the workpieces. This can form a permanent joint. Thermoplastic staking, also known as heat staking, is the same process except that it uses heat to deform the plastic boss. In each example, the protrusion is typically exposed through the hole in the upper workpiece. Additional adhesives are often avoided to secure the workpieces, because they often have a tendency to be expelled through the hole, and may collect on and/or contaminate the die or punch used to deform the protrusion.